Abstract: Apparatus is provided to prevent unauthorized use of a firearm, by locking the trigger in place unless a removable component is available to place the firearm in operative mode. The apparatus includes a locking mechanism comprising a plurality of locking elements, each movable between trigger locking and trigger release positions, and a key guide body provided with a plurality of apertures, each corresponding to one of the locking elements. A grip key adapted for engagement by the hand of a user of the firearm enables the user to readily seat the grip key in a specified position against the firearm, and to detach the grip key therefrom, selectively. A plurality of key elements are mounted upon the grip key, each disposed for insertion through one of the apertures to urge a corresponding locking element to its trigger release position, when the grip key is seated in the specified position.